The CASA definition states that it depends upon whether it is a 3-axis or weight-shift-controlled craft; if the former, it is an ultralight, and if the latter it is a microlight. Ultralights can have cabins now.

Indeed. A friend just assisted in collecting a very well equipped 'ultralight' that was much more expensive and with many higher specifications than an equivalent small airplane. It was made specifically to conform to the class making licensing and flying cheaper and easier.